Part of a rocket, weighing three tons, is thought to have smashed into the far side of the moon at approximately 12:25 p.m. GMT (7:25 a.m. ET), moving at an expected speed of 5,800 mph. (Because of the location of the impact, it could take days or weeks to confirm with satellite images.)

Astronomers have been tracking the rogue rocket part since March 2015, but no one seems entirely certain where it originated. At one point, it was thought to be from a SpaceX rocket, then it was believed to be from a Chinese spacecraft. China has denied responsibility. But astronomer Bill Gray on his Project Pluto blog says, “We now have good evidence that it is actually 2014-065B, the booster for the Chang’e 5-T1 lunar mission,” an experimental robotic spacecraft that China sent to the moon in 2014.

While this rocket—and the dent it leaves on the moon—aren’t worrying scientists too much, it is raising awareness of the amount of debris that is orbiting Earth these days. Experts warn that that “space junk” could eventually collide with something more critical, such as a satellite that provides essential services, like cellular coverage.

This is actually the first unintentional case of man-made space junk hitting the moon, says Gray. (Boosters in the Apollo era were deliberately aimed at the moon to help calibrate seismometers.) However, any fear-mongering that you might have seen that it could affect the lunar orbit is hogwash, he adds.

“I gather there have been some concerns on social media (which, thank the Deity, I’m not on) that the lunar impact might somehow tweak the moon’s orbit,” he writes. “Keep in mind that this is a roughly four-ton object that will hit at 2.58 km/s. The moon is fairly routinely hit with larger objects moving in the ballpark of 10-20 km/s; hence, the craters. It’s well-built to take that sort of abuse.”